The recall of newly learned information declines with increasing age across the adult years. The magnitude of the age effect is influenced by the criterion task used to test recall, such that greater age effects are found in free and cued recall, as compared to recognition. Age effects are also more apparent when the test instructions require the subject to explicitly recall the studied information, rather than using implicit tests to prompt that recall. When the to-be learned information is presented as explicit facts, requiring little inferential processing on the part of the subject, age effects are less apparent. And finally, the use of semantic relationships between newly learned items of information appears to be more spontaneous and beneficial for younger than for older adults. The proposed research will apply an existing model of human memory to the cognitive changes associated with aging. This model describes the effects of prior knowledge that the person brings to the learning situation, and the encoding and retrieval processes used in memory tasks. The model was developed using young adult subjects, and is now sufficiently detailed to apply to memory changes in older adults. The long-term goal of the project is to understand the ways in which older subjects use their prior knowledge to encode and retrieve information. Emphasis will be placed on processes such as the use of prior semantic connections in encoding new information, retrieval inhibition from searching existing knowledge, and accessing concepts across domains of information (i.e., accessing the phonemic code for a word when its semantic code has been retrieved). The initial work on this project will be directed toward understanding cognitive changes in normal healthy elderly subjects. However, this project is also designed to investigate cognitive changes in elderly subjects with intellectual impairment from early dementia and clinical depression. The results of this research will allow us to understand the differences and the commonalities between normal and abnormal cognitive aging, and will have implications for developing techniques for teaching impaired elders.